Obtaining a measurement of a density of a fluid has numerous advantages for various applications. One such application includes, for example, a fermentation of beer. Obtaining density measurements of beer is beneficial in that an indicator for determining whether the beer is properly fermented, i.e., the "Degree Plateau" value, is directly proportional to the density of beer. Obtaining a precise Degree Plateau value is an important indication for obtaining the most favorable results when fermenting beer (or other consumable fluids).
Typically, to measure the density of beer in a beer tank, a beer sample is removed from the beer tank and delivered to a testing facility, where the density of the beer sample is measured. Even though such density measurements may be precise at the time measurements are performed, a transport and a measurement of the sample takes a predetermined amount of time. Therefore, the actual Degree Plateau value of the beer in the tank may not be the most current or the most precise value. Accordingly, the best brewing results may not be achieved using this conventional density measurement method. Another exemplary application in which the determination of the density of the fluid is pasteurization and sterilization of milk.
Other conventional methods and systems for measuring the density in the fluid have also been implemented. One such method provides an assembly having a density sensor and a transmitter. The assembly also includes two tubes which are attached to an external portion of a tank at different fluid levels. The pressure of the fluid in the tank is measured at each fluid level by the pressure sensor, and a pressure signal indicative of the pressure at the particular measured level may be transmitted by the transmitter to a calculating unit. With this method, it may be possible to differentiate between the pressures at the different fluid levels to obtain a density of the fluid. However, this method may provide erroneous readings and measurements depending upon the environmental conditions which may affect the assembly, as well as the pressure sensor and the transmitter. Effectively, the environmental effects (e.g., temperature effects due to sunlight) may effect the measurements of the fluid pressure and the calculations of the density of the fluid. Furthermore, because the sensor/transmitter is externally connected to the tank, the tank must be emptied to access sensor/transmitter parts for scheduled maintenance or cleaning.
Another method for measuring a density in a fluid is described in U.S. Pat. No. 5,211,678. This conventional method provides a reel for lowering a single probe on an electrical cable into a container which maintains the fluid therein. A measurement is taken at the surface of the fluid (in the container), and then at another depth to determine a density of the fluid. However, by using the method described in U.S. Pat. No. 5,211,678, it is possible to obtain inaccurate determination of the density of the fluid because the electrical cable (which is wrapped around a reel) may not be necessarily lowered to predetermined depth levels in the tank. This imprecise procedure of lowering the probe may reduce the precision of the determination of the density of the fluid because an accurate distance between the surface level of the fluid and the predetermined depth levels, thus causing errors in the determination of the fluid density. Furthermore, because of the inaccurate manner in which the reel raises and lowers the cable, it would not be possible to attain reliably consistent density determinations over a number of similar measurements. In addition, this conventional density measurement method provides a delay as the electrical cable is deployed and measurements are taken over several depth levels because only a single probe is utilized. This delay may be substantial over several measurements. Such compounded delays may be unacceptable when an accurate and quick determination of the fluid density is required.
U.S. Pat. No. 4,625,553 describes another conventional system for measuring a density of a drilling mud in an open top tank. This conventional system includes a pair of serially connected pressure sensors internally mounted to inside walls of the tank in the fluid. A constant volume air flow source is connected to an inlet of one pressure sensor, a second pressure sensor is connected to an outlet of the first pressure sensor, and a vent is connected between the second pressure sensor outlet and an external air pressure. A first transducer measures a gas pressure from the air flow source, and a second transducer measures the differential pressure between two pressure sensors. However, when the pressure measurements are taken by these sensors, these measurements may be inaccurate, especially over multiple measurement cycles because the air flow source forcing air throughout the entire system is externally situated, and thus may be subject to varying environmental effects. These environmental effects may cause unreliable measurements and determinations of, for example, pressures and densities of the fluid. Furthermore, because the sensors are mounted to the inside walls of the tank, when it is necessary to perform routine maintenance and cleaning of the tank, the entire tank must be emptied which is inefficient and costly.